Radio printer



Jan. 12, 1937. w. e. H. FINCH 2,067,131

' RADIO PRINTER Filed Nov. 11, 1935 2 Shee'ts-Sheet lllAllll YIVWIVV ATTORNEY Jan. 12, 1937. w. G. H. FINCH RADIO PRINTER Filed Nov. 11. 1935 2 Sheets-Sheet 2 33.3% mmuw 553 mxsl 59/; a/ on.

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S dash $951 $3.52 $3.1m mi Mi 5.55am v; ritual ESQ whim Z r e 3 a 7 a u d l f P I P 0 d m 7 M m n a 7 r H. Um n N D m m N P an electronic amplifier Patented .Fnn. i2, 1937 UNITED STATES- PATENT OFFICE RADIO PRINTER William G. H. Finch, New York. N. Y. Application November 11, 1935, Serial No. 49,221

8Claims.

This invention relates to signalling systems and more particularly, is concerned with electronic amplifier means for positive relay operation at very high speeds and is particularly adaptable for radio printing systems.

Relays and electro-mechanical devices in present use for signal systems in connection with electronic amplifiers, generally function with a magnetic attraction in one direction only of the armature and depend upon spring means or gravity to restore the armature to its original position. The action of such a relay is relatively slow and there accordingly is a definite limitation in the maximum speed of signal transmission, particularly due to the time element required in the return of the armature to its original position. The magnetic action for operating such relays is generally obtained by rectifying the transmitted impulse and further amplifying it with a single ended direct current amplifier. However, such a method is inadequate for the relatively higher speeds of transmission. Y

A repeater relay is used to locally reproduce marking (signal on) and spacing (signal oil) positions in the transmission of telegraphic or printing signals as is well known in the communications art. When the signals are transmitted by means of a carrier wave or by radio, the receiver rectifies the marking signal impulses which are then conducted to a relay wherein an armature is attracted to the marking position. The direct current amplifiers of the prior art were constructed so that the repeater relay was magnetically actuated by said amplifier only during the marking impulse, and depended upon a mechanical biasing means for the spacing" position.

The main object of my present invention is to provide a direct current amplifying circuit for direct actuation of a repeater relay armature for marking and spacing indications thereof.

It is another object of my invention to provide an electronic system for positive diiferential relay actuation at very high speeds.

It is a further object of my invention to provide system for operating a diiferential relay at high speeds without lagging or sticking.

These. and other objects of my invention will become apparent in the description to follow in connection with the drawings in which:

Figure 1 is a circuit diagram of a rectifier together with the direct current push-pull amplifier according to my invention.

Figures 2 and 2a are modifications for connecting the repeater relay to the output circuit of the amplifier of Figure 1.

Figure 3 shows curves used to explain the operation of the rectifier of Figure 1. I

Figure 4 shows curves used to explain the opera- 5 tion of the direct current amplifier of Figure 1.

The marking impulses are generally unidirectional signals of a predetermined .duration according to the speed of transmission required. The spacing impulses of my preferred embodiment correspond to zero current signals. These impulses are transmitted in pre-arranged codes for communication of intelligence or for remote automatic printing actuation. The uni-directional impulses are preferably arranged to operate a constant audio-frequency signal generator to transmit an alternating current signal for the duration of a marking impulse. The signals may alternatively modulate a carrier frequency wave for high frequency transmission, or be directly transmitted over a wire line.

In the preferred embodiment of Figure 1, an audio frequency transformer T--i is shown for coupling received audio frequency signals to a full wave rectifier circuit including thermionic vacuum tubes V-l and V-2. A marking impulse corresponds to a predetermined audio frequency signal impressed upon the input terminals l0 and II to the primary I! of transformer T-l. The audio frequency signal may result from direct wire transmission to terminals in and H, or be the result of detecting a modulated radio frequency carrier wave by a suitable radio receiver.

The terminals l3 and ll of transformer T-l impress the signal upon the grids l5 and ii of the rectifier tubes V-l and V-2 respectively 180 degrees out of phase. A central tap I1 is connected to the negative terminal l8 of the grid biasing battery A, the positive terminal i9 01 which is connected to ground. The cathodes 20 and II are also connected to ground. The grids i5 and I6 are biased to cut-oft. As shown in Figure 3, the alternating current signal input to the grids of the rectifier tubes V-l and V-2 produce a series of alternate half-sine waves in the anode circuits of the vacuum tubes. The full line half waves correspond to'the anode current in one tube, for example, anode 22 of V-I and the dashed line half waves correspond torthe anode 23 current in the other rectifier tube V2.

The anodes 22 and 23 are connected to the common terminal 24 which is by-passed to ground by the by-passing condenser 25. The rectified signal of the rectifier arrangement pro- 55 duces a signal of twice the frequency of the original signal. The condenser 25 shunts the alternating current components of the rectified signal and produces a substantially uniform potential envelope as indicated in Figure 3 in a schematic form. This envelope corresponds in duration to the length of the marking impulse as transmitted. Although I have described two tubes co-acting as a full wave rectifier, one tube or other methods may be used instead for producing uni-directional impulses corresponding to the transmitted signal.

The amplifying stages of the direct current amplifier of my present invention are coupled by circuit means which are described and which is the basis of my co-pending application Serial No. 49,220, filed Nov. 11, 1935.

An anode resistor R-2, is connected to the point 26 which is in turn connected to the rectifier anode at point 24 by miliiammeter M-l. The other end of the resistance R-2 is connected to the point 21 which is connected to the high potential terminal 28 of the common B battery or potential source. The negative terminal of the B battery is connected to ground. The point 26 at anode potential is coupled to the grid 39 of a further amplifying tube V3 by resistor Rl at point 29. The negative terminal 3| of battery C provides sufllcient negative voltage so that the point 29 will operate at the normal operating negative biased voltage for the grid 30 of tube V3 and is connected thereto through the resistor R3. As explained in my co-pending application referred to above a circulating current flows in the series circuit: positive terminal 28 of battery B; resistors R-2, R-I, and R3; negative terminal 3| of battery C; and back to battery B at the ground connection. The cathode of tube V3 is connected to ground. The voltages of batteries B and C are of the same order of magnitude. By suitably proportioning resistors R2, R-l, and R-3 the control grid 30 of tube V3 will be at the proper normal operating negative bias potential with respect to the grounded cathode of tube V3. The grid 32 of the thermionic vacuum tube V5 is connected ,to the point 29' which is at the same potential as the point 29, being connected directly thereto. The input circuits of the two tubes V3 and V5 are accordingly-connected in parallel.

Another amplifying stage V4 is cascaded from the tube V3 and coupled in a manner similar to that hereinbefore described. The resistors R-4, R-5 and R,6 form the coupling means between the anode33 of tube V3 and the grid 34 of the tube V4. The common B and 0 batteries are utilized. A milliammeter M-'-2 is provided in series with the anode 33.

The resistor R'I is the load resistor for anode 35 and resistor R-8 is the load resistor for anode 36. These anodes are connected to the common point 31 which is in turn connected to the point 21' which connects to the positive terminal of the B battery. The grid bias of tubes V3 and VS are adjusted so that normal space current flows through their anode circuits during no signal input which currents will be indicated by their meters M2 and M4. The grid 34 of vacuum tube V-4, however, is biased to cut-off so that no current flows through ammeter M--3 during no signal input. The operation of my invention is as follows:

when no signal is impressed on the terminals in and II, no current will pass through the rectifier output meter Ml, and the point 26 will be at its normal potential. No signal impulse is accordingly transmitted to the tubes V3 and V--5 and therefore normal anode current will flow through them as indicated by meters M2 and M-4. Since the tube V-4 is biased to cutofl, no current will flow through the meter M3. The current through the anode circuit of V5 will cause a potential drop across the anode resistor R-8 and the point 38 will be at a lower potential than point 31. Since no current flows through ammeterM-3, there is no voltage drop across resistor R1 due to anode currents and the potential of point 39 is closer to the potential of point 31 than is that of point 38.

During no signal or spacing" condition of the system, a difference of potential accordingly exists between points 38 and 39, 38 being at a lower potential than 39. A resistance R9 is connected between these points and a potential difierence accordingly exists across this resistance R,9. A repeater relay 40 is also connected between points 38 and 39, and the resultant difference of potential between terminals 38 and 39 will accordingly send current in a predetermined direction through the relay 40 which would correspond to a spacing impulse to correspond to no signal impulse at the input terminals I 0 and II.

When a sinusoidal signal occurs at the input terminals l0 and H, of the Figure 1, it is rectified by the rectifier tubes Vi, V2 as hereinabove explained in connection with Figure 3 to produce a uni-directional impulse corresponding to the envelope drawn in Figure 3. This uni-directional impulse causes a corresponding current flow through meter Ml and resistance R--2. A potential drop accordingly occurs across R2 to reduce the potential of point 26 from its normal original value. The point 29 which is connected to the grid 30 of the tube V3 is accordingly reduced in potential from its normal value during the signal-on" period.

In Figure 4, curve I shows the wave form of the negative impulse transmitted to the grid 39 of tube V3. Since the input of vacuum tube V5 is connected in parallel with the vacuum tube V3, the same signal is impressed upon its grid 32. No attempt to illustrate relative potential magnitudes has been made.

The grids 30 and 32 accordingly are made more negative during signal on" or marking". The anode currents of the tubes V3 and V--5 are correspondingly decreased, producing a smaller voltage drop across resistor lit-8 than existed during normal or signal off conditions. The plate potentials of the vacuum tubes V3 and V5 are thereby increased. The relative increase of the anode or plate potential of the tubes V3 and V--5 during signal-on condition is indicated by curve 11 of Fig. 4. The vertical axis represents increase of signal-on plate potential above that of the normal or signaloff potential. The wave form or envelope of the signal impulse of curve 11 is similar to that of the grid signal curve I. The voltage of point 38, connected to anode 36 of tube V--5 correspondingly increases in magnitude during the signal-on" condition.

The increased potential of anode 33 is transmitted to the grid 34 of vacuum tube Vl by the resistance coupling network R4, R--5 and R-B. The rise in the grid 34 potential from its cut-off value causes anode current to flow in anode 35 and also the resistance R-l, and is aoomsi' indicated in meter bit-3. A potential drop takes place across the resistance R-l, and the potential of point 29 is decreased. Curve III of Figure 4 indicates the relative plate 85 oi tube V4 potential decrease, having the same transmitted wave form or envelope as curves I and II. The magnitude of this potential is not illustrated to any relative scale.

A signal or marking impulse accordingly increases the potential oi point 88 and decreases that of point 39 with respect to constant potential point 31 producing an efiective reversal in the voltage between points 38 and 39 as compared to no signal or "spacing" condition. The current through the polarized relay 40 is therefore reversed for the marking impulse and attracts the armature to the marking position.

A positive electrical actuation of the relay to K is accordingly obtained for marking and spacing signals.

In Figure 2, I have illustrated a modification of the relay and its connection to the output of the circuit of Figure 1. The polarized relay 4| has a center tap connecting to the constant B potential point 31. During signal-ofi' or spacing" condition, a smaller difierence in potential exists between points 31 and 38 than between points 31 and 39 since anode current flows in resistor R8 to cause a voltage drop therein. Point 38 will have a lower potential than point 39 and current will fiow through relay GI in a direction to actuate the spacing" relay contact. When a marking impulse occurs, the current reverses in a direction through relay M to actuate the marking contact. The action of the relay M is similar to that of relay 42.

A further modification is shown in Figure 2a. The polarized relay 42 is connected in the anode circuits of tubes V-4 and V5. During signal all, current fiows in the tube V-- anode circuit and the corresponding portion of relay 42 winding to attract its armature to the spacing position. During signal on, the other winding section is actuated to reverse the position of the relay d2 armature to the marking position.

Although I have described preferred embodiments for positively and electronically actuating a. diiferential repeating relay to marking and spacing positions for controlling a local printing apparatus, other uses and modifications will be evident to those skilled in the art.

My present invention adapts the direct current amplifying circuit of my co-pending application hereinabove referred to for a push-pull output. The signals are reversed 180 degrees in phase by each amplifier vacuum tube stage. I accordingly provide two cooperating direct current amplifying systems having a common input circuit, one of the amplifying systems having one more amplification stage than the other. Although I have shown two stages in the V-3 and V4 system and one stage in the V5 system, correspondingly more stages may be used.

The function of the one extra stage is to reverse by 180 degrees the phase of the uni-directional signals at the output of one of the amplifying systems with respect to the other. The signals at points as and as are accordingly 180 de grees out of'phase as in an ordinary push-pull circuit. The bias voltages applied to the various grids may have any desired values. The bias voltages of the output tubes corresponding to tubes V-l and V5 may both be adjusted to cut-off and the circuit will correspond to a class B push-pull direct current amplifier and any preferred translating device may be connected thereto. The circuit may be designed to produceequal over all amplification between the common input point 28 and the output points 38 and 38 by proper design of the two cooperating reversed phase amplifier sections.

I claim:

1. In a signalling system a first direct current amplifier comprising a plurality of stages; a second direct current amplifier comprising one stage less than said first amplifier, the input circuits oi. said first and second direct current amplifiers being connected in parallel; each stage of said amplifiers including a cathode. anode and control electrode; a common anode potential source for all of said stages; circuit connections for maintaining all of said cathodes at substantially the same potential; means including a second common potential source for maintaining each control electrode at an individual biasing potential with respect to its associated cathode; and a translating device, the opposite terminals of said device being connected to respective anodes of the last stage of each of said amplifiers.

2. In a signalling system a first d rect current amplifier comprising two stages; a second direct current amplifier comprising one stage, the input circuits of said first and second direct current amplifiers being connected in parallel; each stage of said amplifiers including a cathode, anode and control electrode; a common anode potential source for all of said stages: circuit connections for maintaining all of said cathodes at substantially the same potential; a conductive connec tion including a first impedance element from the anode of the first. stage of said first amplifier to the control electrode of the next succeeding stage; a second common potential source; circuit connections including'a second impedance element extending from all anodes to a terminal of said anode source; circuit connections including a third impedance element extending from all control electrodes to a terminal of said second source; all of said circuit connections controlling the application of the anode potential to their respective anodes and maintaining a predetermined bias potential on their respective control electrodes with respect to their individual cathodes; a translating device, the opposite terminals of said device being connected to respective anodes of the output of each of said amplifiers.

3. In a signalling system a first direct current amplifier comprising a plurality of stages; a second direct current amplifier comprising one stage less than said first amplifier. the input circuits of said first and second direct current amplifiers being connected in parallel; each stage or said amplifiers including a cathode, anode and control electrode; a common anode potential source for all of said stages; circuit connections for maintaining all of said cathodes at substantially the same potential; a second common potential source; circuit connections associated with each amplifying stage and said sources for controlling the anode voltages of said stages and for maintaining a predetermined bias on said control electrodes with respect to their respective cathodes.

4. In a signalling system a first direct current amplifier comprising a plurality of stages; a second direct current amplifier comprising one stage less than said first amplifier, the input circuits 01' said first and second direct current amplifiers being connected in parallel; each stage of said amplifiers including a cathode, anode and ond direct current amplifier comprising one stage less than said first amplifier, the input circuits of said first and second direct current amplifiers being connected in parallel; each stage oi said amplifiers including a cathode, anode and control electrode: a common anode potential source for all of said stages; circuit connections for maintaining all of said cathodes at substantially the same potential; a second common potential source; circuit connections including an impedance element extending from each of said anodes to a terminal oi said anode source; circuit connections including an impedance element extending irom the control electrodes of each of said stages to a terminal of said second source, saidcircuit connections controlling the applica-- tion of the anode potential to their respective- ,anodes and maintaining a predetermined bias potential on their-respective control electrodes.

8. In a signalling system a first direct current itiriplitler comprising a plurality of stages; a second direct current amplifier comprising one stage less than said first amplifier, the input circuits of said first and second direct current amplifiers being connected in parallel; each stage of said amplifiers including a cathode, anode and controlelectrode; a common anode potential source for all of said'stages; circuit connections for maintaining all of said cathodes at substantially the same potential, the control electrodes of the first stage of said amplifiers being interconnected; a rectifier for supplying uni-directional signals to said input circuits, means including a second common potential source for maintaining each control electrode at a negative biasing potential with respect to its associated cathode;

ace-2, 101- and a translating device, the opposite of said device being connected to respective anodes oi the last stage of each oi said amplifiers.

7. In a signalling system a first directcurrent amplifier comprising a plurality oi stages; a second direct current amplifier comprising one stage less than said first amplifier. the input circuits of said first and second direct current amplifiers being connected inparallel; each stage of said amplifiers including a cathode, anode and control electrode; a common anode potential source for all of saidstages; circuit connections for maintaining all of said cathodes at substan-' tially the same potential; means including a secand common potential source for maintaining each control electrode at an individual biasing potential with respect to its associated cathode;

a translating device comprising an impedance Y element havinr a midpoint connection, the 'W site terminals oi said device being connected to respective anodes oi the last stageoi' each oi said amplifiers and saidmidpoint connection connected to said anode potential source.

8.1nasignallingsystemafirstdirectdurrent amplifier comprising a plurality oi stages; a second direct current amplifier comprising one stage less than saidfirst amplifier, the input circuits of said first'and second direct current amplifiers being connected in parallel; each stage of. said amplifiers including a cathode, ans ode and control electrode; a common anode potential source for all of said stages; circuit connections for maintaining all of said'cathodes at substantially the same potential, the control electrodes of the first stage of said amplifiers being interconnected; a rectifier for supplying uni-directional signals to said input stages; means including a second common potential source for maintaining each control electrode at an individual biasing potential with respect to its associated cathode; a translating device comprising an impedance element having a midpoint connection, the opposite terminals of said device being connected-to respective anodes of the last stage of each of said amplifiers and said midpoint connection being connected to said anode potential source.

WILLIAM G. H. FINCH. 

